The present disclosure relates generally to liquid crystal displays (LCDs) and, more specifically, to oxide thin-film transistors (TFT) that may be used to form pixels of such LCDs.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Flat panel displays, such as liquid crystal displays (LCDs), are commonly used in a wide variety of electronic devices, including such consumer electronics as televisions, computers, and handheld devices (e.g., cellular telephones, audio and video players, gaming systems, and so forth). Such display panels typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods. In addition, such devices typically use less power than comparable display technologies, making them suitable for use in battery-powered devices or in other contexts where it is desirable to minimize power usage.
LCD devices typically include picture elements (image pixels) arranged in a matrix to display an image that may be perceived by a user. The matrix, sometimes called an array, includes rows and columns of thin-film-transistors (TFTs) arranged adjacent to a layer of liquid crystal material, wherein the each TFT represents an image pixels. Individual pixels of an LCD device may variably permit light to pass when an electric field is applied to a liquid crystal material in each pixel, which may be generated based upon a voltage difference between a pixel electrode and a common electrode. The TFT of the pixel passes the voltage difference onto a pixel electrode when an activation voltage is applied to its gate and a data signal voltage is applied to its source. By controlling the amount of light that may be emitted from each pixel, the LCD, in conjunction with a color filter array, may cause a viewable color image to be displayed.
However, a parasitic capacitance between the gate line supplying a gate activate voltage and other components of the pixel may result in the occurrence of certain visual artifacts, such as image sticking (e.g., parasitic capacitance between the gate line and the pixel electrode and/or drain of the TFT) and/or green tinting (e.g., DC voltage coupling effect between gate activation signal and the liquid crystal material and/or polyimide materials used for liquid crystal alignment. Such visual artifacts may reduce the accuracy of the display. Additionally, in some LCD devices, certain properties of the TFTs cause large RC loading in the gate lines and/or common electrodes. This may reduce TFT switching performance, which may also cause visual artifacts. These problems may become more pronounced as LCDs increase in resolution, with the pixels becoming more densely-packed.
Further, in existing LCDs, TFTs may include an active layer that is typically fabricated using silicon-based materials, such as amorphous silicon (a-Si), poly-silicon (poly-Si), or microcrystalline silicon. Such silicon-based materials typically have a scaling limit, meaning that once they are scaled down to a certain size, they generally cannot be reduced any further in size without affecting operation. Additionally, the dimensions of an opaque black mask portion of a color filter array are generally selected so that the TFTs, gate lines, and source lines are covered by the black mask when viewed from the front side of the LCD. Thus, since light emitted from a backlight of the LCD device cannot transmit through the black mask, the overall transmittance of the LCD is at least partially limited by the dimensions of the black mask, which, in turn, is limited by the size of the TFTs, gate lines, and data lines.